In the construction of turbo machines, especially in the construction of steam turbines, steam at temperatures lying below the temperature of live steam under live steam pressure is required for cooling regions that are subjected to high thermal stress. The live steam pressure is the pressure of a flow medium entering the inflow region of a turbo machine. The live steam temperature is correspondingly the temperature that a flow medium has at the inlet into a turbo machine.
In today's turbo machines, cooling steam with the characteristic variables described above of temperature and pressure is not produced by the machine itself.
The cooling steam required is generally supplied to the turbo machine through a separate line. In the case of turbo machines with multi-stage superheater stages, the cooling steam is usually removed from an associated boiler upstream of the last superheater stage and passed to the turbo machine in a separate line. The disadvantage of this solution is that a separate line causes additional costs. In addition, a direct dependence on the boiler arises to the extent that the dimensioning of the cooling steam system depends on the boiler parameters and that failure of the cooling steam supply likewise leads to failure of the cooling.